It has been suggested that pathological consequences of HIV are likely resulted from the effect of the viral proteins produced intracellularly following HIV infection. Such phenomena have also been reported for AIDS in mouse, for instance, the gag product from a defective retrovirus Du5H has been implicated as a possible pathogenic determinant of the syndrome. We propose to examine these effects using a mouse placenta/embryo culture system. From years of work, it is now established that by supplying specific growth medium, a large proportion of mouse blastocysts is able to differentiate properly in vitro to at least the limb bud stage. At this stage, blood circulation in the yolk sac, forelimb buds, primordia of liver, pancreas, lung, and neural tissues can readily be observed (Hsu, Y. C., Dev. Growth & Diff. 32, 131-137 (1990)). Our laboratory has recently found that endogenous retroviral IAP genes and IAP LTR promoted cellular genes are selectively expressed in parietal and visceral endoderms of yolk sac and in chorionic ectoderm of placenta of 13.5 day mouse conceptus. Therefore these tissues may also serve as target sites for the synthesis of viral proteins if IAP LTR can be used to drive the transcription of HIV genes. To test this possibility, and to search for the effect of viral proteins on developing embryos, coding sequences of HIV genes (gag, pol, env and TAT, Rev) and Du5H gag gene will be structurally linked to active IAP LTR promoters specific for their expressions in tissues of trophectoderm/primitive endoderm lineages. Promoter linked coding sequences will next be incorporated into retroviral vector and used to infect early mouse embryos isolated from mothers of C57B1/6, FVB/N mice and transgenic mice (FBV/N/HIV) carrying a latent HIV proviral genome. Developmental and biochemical studies of infected embryos will be followed. The effects of TAT protein and Rev protein on cellular proliferation and HIV latency in embryos of FVB/N/HIV mice will also be analyzed.